Duncan
was the son of Malcolm II's eldest daughter Bethoc and her husband Crinan,
Lay Abbot of Dunkeld. He was about 33 when he succeeded his grandfather.
Married to a cousin of Siward, Earl of Northumberland, he may have favoured
southern ways and this is perhaps why he became unpopular with his subjects.

He was not the best tactician and in 1038 he marched south to besiege Durham
but he was beaten off, with heavy losses. Duncan attempted to impose his over lordship over Moray (an
independent dynasty) by military force. He was then twice defeated by the
Earl of Orkney's son, Thorfinn, before being killed in battle by Macbeth,
one of his commanders, near Elgin,
Morayshire on 14 August 1040 and is at rest with other Scottish in Iona.

William Shakespeare based his play, Macbeth, one of his greatest tragedies,
upon a distorted version of these events which he found in Raphael
Holinshed's 'Chronicle of Scottish History.' The only kernel of historical
truth in the play is Duncan's death at the hand of Macbeth. From this fact,
Shakespeare drew his portrait of ambition leading to a violent and tragic
end.